page_title: Twilight
section_title: Duration
hierarchical_section_title: Twilight / Duration
caption_attribution_description: English: Carpet Plot showing Elevation of sun above horizon North of the Polar Circle
context_page_description: Twilight on Earth is the illumination of the lower atmosphere when the Sun is not directly visible because it is below the horizon. Twilight is produced by sunlight scattering in the upper atmosphere, illuminating the lower atmosphere so that Earth's surface is neither completely lit nor completely dark. The word twilight is also used to denote the periods of time when this illumination occurs.
  The lower the Sun is beneath the horizon, the dimmer the twilight. When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers, who sometimes refer to it as "sweet light", and painters, who often refer to it as the blue hour, after the French expression l'heure bleue.
  Twilight should not be confused with auroras, which can have a similar appearance in the night sky at high latitudes.
context_section_description: The duration of twilight depends on the latitude and the time of the year. The apparent travel of the sun occurs at the rate of 15 degrees per hour (360° per day), but sunrise and sunset happen typically at oblique angles to the horizon and the actual duration of any twilight period will be a function of that angle, being longer for more oblique angles. This angle of the sun's motion with respect to the horizon changes with latitude as well as the time of year (affecting the angle of the Earth's axis with respect to the sun).
  At Greenwich, England (51.5°N), the duration of civil twilight will vary from 33 minutes to 48 minutes, depending on the time of year. At the equator, civil twilight can last as little as 24 minutes. This is true because at low latitudes the sun's apparent movement is perpendicular to the observer's horizon. But at the poles, civil twilight can be as long as 2–3 weeks. In the Arctic and Antarctic regions, twilight (if there is any) can last for several hours. There is no astronomical twilight at the poles near the winter solstice (for about 74 days at the North Pole and about 80 days at the South Pole). As one gets closer to the Arctic and Antarctic circles, the sun's disk moves toward the observer's horizon at a lower angle. The observer's earthly location will pass through the various twilight zones less directly, taking more time.
  Within the polar circles, twenty-four-hour daylight is encountered in summer, and in regions very close to the poles, twilight can last for weeks on the winter side of the equinoxes. Outside the polar circles, where the angular distance from the polar circle is less than the angle which defines twilight (see above), twilight can continue through local midnight near the summer solstice. The precise position of the polar circles, and the regions where twilight can continue through local midnight, varies slightly from year to year with Earth's axial tilt. The lowest latitudes at which the various twilights can continue through local midnight are approximately 60.561° (60°33′43″) for civil twilight, 54.561° (54°33′43″) for nautical twilight and 48.561° (48°33′43″) for astronomical twilight.
  Lowest latitude can be observed at local midnight in month of April:
  Civil Twilight: 69°N
  Nautical Twilight: 63°N
  Astronomical Twilight: 57°N
  Lowest latitude can be observed at local midnight in month of May:
  Civil Twilight: 62°N
  Nautical Twilight: 56°N
  Astronomical Twilight: 50°N
  Lowest latitude can be observed at local midnight in month of October:
  Civil Twilight: 69°S
  Nautical Twilight: 63°S
  Astronomical Twilight: 57°S
  Lowest latitude can be observed at local midnight in month of November: 
  Civil Twilight: 62°S
  Nautical Twilight: 56°S
  Astronomical Twilight: 50°S
  These are the largest cities of their respective countries where the various twilights can continue through local solar midnight:
  Civil twilight from sunset to sunrise: Tampere, Umeå, Trondheim, Tórshavn, Reykjavík, Nuuk, Whitehorse, Anchorage, Arkhangelsk and Baltasound. In the Southern Hemisphere, there are no major permanent settlements far enough South to experience this.
  Nautical twilight from civil dusk to civil dawn: Moscow, Vitebsk, Vilnius, Riga, Tallinn, Wejherowo, Flensburg, Helsinki, Stockholm, Copenhagen, Oslo, Newcastle upon Tyne, Glasgow, Belfast, Letterkenny, Petropavl, Grande Prairie, Juneau, Ushuaia, and Puerto Williams.
  Astronomical twilight from nautical dusk to nautical dawn: Hulun Buir, Erdenet, Nur-Sultan, Samara, Kiev, Minsk, Warsaw, Košice, Paris, Dublin, Zwettl, Prague, Stanley (Falkland Islands), Berlin, Luxembourg City, Brussels, Amsterdam, London, Cardiff, Calgary, Unalaska, Bellingham (largest in the continental USA), Rio Gallegos, and Punta Arenas.
  Major cities that near astronomical twilight from nautical dusk to nautical dawn: Saguenay (48°25′0"N), Brest (48°23′26"N), Thunder Bay (48°22′56″N),  Vienna (48°12′30″N), Bratislava (48°8′38″N), Munich (48°8'0"N)
  Although Helsinki, Oslo, Stockholm, Tallinn, and Saint Petersburg also enter into nautical twilight after sunset, they do have noticeably li
caption: Carpet plot of sunshine at latitude 70 North
exif: {}